Joy found in single entry (4)
I believe the answer is:
glee
'joy' is the definition.
(I know that joy can be written as glee)
'in single entry' is the wordplay.
'in' indicates the answer is hidden within the clue.
'GLEE' can be found hidden inside 'single entry'.
'found' acts as a link.
(Other definitions for glee that I've seen before include "Great delight; part song" , "Lively or triumphant joy" , "Jewelled headband" , "(Malicious) satisfaction" , "Part-song for male voices - delight" .)